Monday, August 29, 2011

The Curious Link Between H1N1 Flu and Narcolepsy

A swell in new cases of narcolepsy in China followed seasonal patterns of flu, including H1N1, according to a recent study led by Dr. Emmanuel Mignot of the Stanford University School of Medicine. The new cases appear to be associated with flu infection itself, not with flu vaccinations.

A peak in cases of narcolepsy — an autoimmune disease that causes people to fall asleep suddenly — occurred about five to seven months after a peak in cold and flu cases in the country, the study found. Onset in the spring was seven times more common than in the winter.

Researchers believe that people have a genetic predisposition to narcolepsy, which may be triggered by some environmental factor, such as an upper airway infection. Reported the New York Times:

Narcolepsy and a related but even rarer illness, cataplexy — a tendency to collapse when swept by strong emotions — are caused by the death of brain cells that secrete hypocretin, which regulates sleep. Those cells, Dr. Mignot explained, are probably killed by autoimmune reactions that stem from winter infections like flu and strep throat.

For several years after the 1918 Spanish flu pandemic, medical authorities described a seasonal somnolence they called "encephalitis lethargica."

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